By Lisa Rapaport

(Reuters Health – Healthcare workers may not be using the right amount of hand sanitizer or letting it dry on their hands long enough to achieve maximum protection against the spread of germs, a recent study suggests.

Researchers did lab tests to see how long different amounts of gel and foam versions of alcohol-based hand sanitizer took to dry on nine volunteers’ hands. In the test of 0.75-milliliter, 1.5ml, 2.25ml and 3ml dollops, smaller amounts of sanitizer sometimes dried within the 20-30 second time frame recommended by the World Health Organization for optimal effectiveness, but none of the products dried that fast when the largest amounts were used.

“Some people with larger hands may need a bit more product, and this paper demonstrates that the amount being dispensed in many standard dispensers is not providing the ideal amount of product,” said Elaine Larson, professor emerita at the Columbia University School of Nursing in New York City.

In the study, volunteers needed at least 2.25ml of sanitizer, and sometimes more, for optimal coverage on the front and back of hands.

Gels dried faster than foams in general, with 3ml of gel taking 37 seconds to dry while the same amount of foam took an average of 57 seconds – both times exceeding the WHO recommendation.

Researchers also looked at how much hand sanitizer health workers applied in real-world settings and compared how quickly workers thought it dried to actual drying times. Generally, workers thought sanitizer dried much faster than it really did.

“Staff have an unrealistic idea of the timing for hand hygiene,” Larson, who wasn’t involved in the study, said by email. “Alcohol is only active when it is wet so drying time is important.”

It’s possible workers think drying times are shorter than they really are because they’re using less product than they should be, aided in part by dispensers that release too little sanitizer in a single pump, the study team speculates.

“If a drying time is too short, sufficient effect cannot be exhibited,” said Dr. Ryohei Hirose, a researcher at Kyoto Prefectural University of Medicine in Japan who wasn’t involved in the study.

But health workers might think two pumps of sanitizer is more than they need, the researchers write in the American Journal of Infection Control. That means the amount dispensed might need to increase to ensure that a single pump releases the optimal amount of sanitizer, the study team concludes.

“A dispenser volume to achieve 20-30 seconds of drying time as per WHO recommendations is required for effective hand hygiene,” Hirose, who wasn’t involved in the study, said by email.

To fight germs effectively, alcohol-based hand sanitizers should contain at least 60% alcohol, according to the U.S. Centers for Disease Control and Prevention. People should cover all surfaces of the hands, including spaces between fingers, and rub hands together for around 20 seconds, until hands feel dry, according to the CDC.

When hands are dirty or greasy, people should ideally wash hands with soap and water, and only use sanitizer when handwashing isn’t an option, the CDC advises.

SOURCE: American Journal of Infection Control, online January 13, 2020.